<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="cssTest"></div>
</body>
</html>
<style>
  #cssTest{
	float:left;
	width:200px;
	height:200px;
	border:2px solid red;
	position:relative;
	left:20px;
	top:20px;
}
#cssTest:before{
	content:"";
	border:20px solid red;
	border-top-color:transparent;
	border-right-color:transparent;
	border-bottom-color:transparent;
	width:0px;
	height:0px;
	position:absolute;
	left:202px;
	top:50px;
}
#cssTest:after{
	content:"";
	border:19px solid #fff;
	border-top-color:transparent;
	border-right-color:transparent;
	border-bottom-color:transparent;
	width:0px;
	height:0px;
	position:absolute;
	left:200px;
	top:51px;
}
</style>